EXPRESSION OF THE STA2 GLUCOAMYLASE GENE OF SACCHAROMYCES-CEREVISIAE IN BREWERS-YEAST

Two fragments of DNA containing the Saccharomyces cerevisiae STA2 gluc oamylase gene, with differing lengths of 5' non-coding DNA, were separ ately subcloned into a yeast centromeric plasmid. Of these two subclon es, only the shorter one (containing 127 base-pairs of 5' non-coding D NA) was able to confer glucoamylase production on a standard laborator y strain of S. cerevisiae. The longer subclone (containing 465 bp of 5 ' non-coding DNA) did, however, confer glucoamylase production on a st rain of S. cerevisiae lacking a functional STA10 gene (which encodes a repressor of STA2 gene expression). All-yeast plasmids tacking bacter ial DNA were constructed from the two STA2 subclones for the transform ation of a lager brewing yeast. Only the shorter STA2 subclone conferr ed glucoamylase activity on this yeast. The level of enzyme activity w as comparable to that produced by the same yeast strain containing STA 2 expressed from the PGK1 (that is, PGK1) promoter.